1a.Objectives (from AD-416):
The current specific aims are:.1)Use genotyping and phenotyping tools to determine if there are host genes that control resistance/susceptibility to porcine respiratory and the reproductive syndrome virus (PRRSV) infection;.2)Verify genetic variation in response to PRRSV, via improved health, survivability and growth; and.3)Identify relative importance of different phenotypes, and their heritability, that predict response to PRRSV infection.

1b.Approach (from AD-416):
This is a multi-year project that is funded by a consortium representing NPB, USDA, universities and private companies. The consortium represents the first-of-its-kind approach to food animal infectious disease research. The objective of this cooperative research project is to assess the genetic basis of pig responses to porcine reproductive and respiratory syndrome virus (PRRSV) infection, an infection which causes pneumonia and growth retardation in pigs, affecting the respiratory mucosa. The project uses a Nursery Pig Model to assess pig resistance/susceptibility to primary PRRSV infection. Results from the first year have affirmed that there are genetic components involved in controlling the effectiveness of pig responses to PRRSV infection. By continuing these studies, the plan is to test a larger number (1,500 total over 4 years) of PRRSV infected pigs. Data collected, using a series of defined assays, stored samples for later work and collated data in the PHGC database will enable researchers to verify important genotypes and phenotypes that predict resistance, tolerance or susceptibility to PRRSV infection.

3.Progress Report:

The PRRS Host Genetics Consortium (PHGC) has now completed 12 infection trials to assess the role of host genetics in Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) resistance. With funding from the National Pork Board (NPB), and more recent funding from Genome Canada, ARS scientists at Beltsville, MD (BARC) are working with Kansas State University (KSU) and Iowa State University (ISU) to collect samples for a detailed phenotype of the role of pig genetics in resistance to PRRSV infection. Using a Nursery Pig PRRSV infection model, 12 infection trials of 200 pigs each have been completed at the KSU biosecure animal facility, thus well surpassing the original goal of testing 1,500 pigs. High health pigs donated by commercial breeding companies were infected with a 1998 PRRSV isolate for the first nine trials; whereas a more recent, 2006 PRRSV isolate was used for PHGC trials 10-12. Blood was collected at 10 time-points for each pig, resulting in 20,000 each of sera (for virus and immune proteins) and whole blood samples (for RNA). In addition, tissue from tonsils (for virus persistence tests), and ears (for DNA) were collected and archived along with sera and blood samples in numerous freezers at KSU and BARC. At BARC this year, the last 100 genomic DNA samples were prepared for completing the genotyping of PHGC1-8. All PHGC data is being stored in the secure, password protected PHGC database at ISU: http://www.animalgenome.org/lunney/index.php. Access to the PHGC database is open to Consortium members who have signed a Cooperative Research and Development Agreement (CRADA) Material Transfer Agreement (MTA) #58-3K95-9-1319 organized by BARC. Other grants associated with this effort and with this ARS project have funded completion single nucleotide polymorphism chip genotyping of all PHGC pigs and analyses of whole blood RNA and serum for differences in gene and protein expression during the infection. The PHGC and related projects will help identify the role of host genes in PRRSV resistance or susceptibility, as well as in the ability of some pigs to grow normally despite being PRRSV infected. This project has already revealed new genetic regions that are associated with PRRS resistance or alternately with increased PRRS susceptibility. Results should help pig breeding companies to identify and provide more disease resistant pigs to producers.